The use of radiation therapy to treat cancer is well known. Typically, radiation therapy involves directing a beam of high energy proton, photon, ion, or electron radiation (“therapeutic radiation”) into a target or target volume (e.g., a tumor or lesion).
Before a patient is treated with radiation, a treatment plan specific to that patient is developed. The plan defines various aspects of the therapy using simulations and optimizations based on past experiences. In general, the purpose of the treatment plan is to deliver sufficient radiation to the target while minimizing exposure of surrounding normal, healthy tissue to the radiation.
The planner's goal is to find a solution that is optimal with respect to multiple clinical goals that may be contradictory in the sense that an improvement toward one goal may have a detrimental effect on reaching another goal. For example, a treatment plan that spares the liver from receiving a dose of radiation may result in the stomach receiving too much radiation. These types of tradeoffs lead to an iterative process in which the planner creates different plans to find the one plan that is best suited to achieving the desired outcome.
A recent radiobiology study has demonstrated the effectiveness of delivering an entire, relatively high therapeutic radiation dose to a target within a single, short period of time. This type of treatment is referred to generally herein as FLASH radiation therapy (FLASH RT). Evidence to date suggests that FLASH RT advantageously spares normal, healthy tissue from damage when that tissue is exposed to only a single irradiation for only a very short period of time. FLASH RT thus introduces important constraints that are not considered in or achieved with conventional radiation treatment planning.